1. Field of the Invention
This invention relates to transmission of energy at microwave frequencies and more particularly to providing power from a single signal source to a plurality of loads and from a plurality of signal sources to a single load.
2. Description of the Prior Art
A device, such as a transistor, has an undesirably low capability for providing power at microwave frequencies. Because of the low power capability, a power amplifier in the microwave art is usually comprised of a plurality of transistors connected in parallel, whereby each of the transistors contributes a portion of power provided to a single load.
The transistor inherently has input and output impedances that are low in comparison with the characteristic impedance of a transmission line, such as a waveguide, for example. Since the amplifier is comprised of the plurality of transistors connected in parallel, the amplifier has input and output impedances (referred to as terminal impedances) that are much lower than the characteristic impedance. Therefore, there is usually a severe mismatch between a terminal impedance and the characteristic impedance.
The severe mismatch is usually obviated by a connection of the amplifier to the waveguide through an impedance transformation device. The transformation device typically has a bandwidth that is inversely related to a ratio (called an impedance transformation ratio) of the characteristic impedance to the terminal impedance. Therefore, because of the severe mismatch, the transformation device introduces a substantial limitation on the bandwidth of power transmitted therethrough. Hence, there is a need for a power amplifier that can be used without introducing such a bandwidth limitation.